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Pre-filtering on shadow areas

The noise level of paper_texture & screening is directly proportional to darkness of images. thus darken only filtering & greyscale mask with inversion helps to avoid overfiltering.



#1 is the result of above post

First, duplicate a layer, then remove CrCb noises by your favorite filter (#2). it doesn't show the effect obviously, but it's essential.

2nd, duplicate 2nd layer again then set layer mode darken (#3)

3rd, apply Neatimage strongly at 3rd layer.
if a scan have paper_texture, up low-freq overly with very low-freq. the preview (#4) looks overfiltered, but no problem because the result will become #5 due to darken mode.

After merged 2nd & 3rd layers, add a back ground grayscale mask with inversion. mechanism is as same as the above post, only difference is it's with inversion (#6)

This is the end of pre-filtering. but it still needs main filtering.
after main filtered image is #7.
even though, It's not still finished. I have to do manual masking, dust erasing, smearing halo artifacts, e.t.c..